How to connect a VU-Meter to amplifier output channels

[Tazio]

HI everybody,
this is my very first DIY audio system. I'm quite satisfied of it.
But I have a problem I can't understand how to work out:
to connect the VU-Meter I used the circuit taken from this page https://www.giangrandi.ch/electronics/vu-meter/vu-meter.shtml.
After quite some attempt adjusting the resistors value I could get it to work quite well.
BUT I it is connected to one channel only and I'd like to connect it to both channels.
My question is: can I duplicate the circuit and connect both to the same VU-Meter terminals?
Is there a better way to do that?

 

[MaxwellsEq]

HI everybody,
this is my very first DIY audio system. I'm quite satisfied of it.
But I have a problem I can't understand how to work out:
to connect the VU-Meter I used the circuit taken from this page https://www.giangrandi.ch/electronics/vu-meter/vu-meter.shtml.
After quite some attempt adjusting the resistors value I could get it to work quite well.
BUT I it is connected to one channel only and I'd like to connect it to both channels.
My question is: can I duplicate the circuit and connect both to the same VU-Meter terminals?
Is there a better way to do that?

If you take your drawing and erase the meter, you will notice that you appear to be wiring the output of one amplifier into the output of the other. That's not good.

However, if the meter and associated buffer or resistor matrix are very high impedance then the risk is relatively low. Ideally you would pick up the signal closer to the input of the amplifiers than at the output.

 

[Zek]

I'd like to connect it to both channels.

What is the point of connecting both channels to one VU meter?
Isn't it better for each channel to have its own VU meter?

 

[Tazio]

If you take your drawing and erase the meter, you will notice that you appear to be wiring the output of one amplifier into the output of the other. That's not good.

However, if the meter and associated buffer or resistor matrix are very high impedance then the risk is relatively low. Ideally you would pick up the signal closer to the input of the amplifiers than at the output.

Hi, and thank you for replying. If I'm not wrong, Giangrandi's circuit is intended to pick up the signal from the amplifier output and it's resistance is sufficiently high not to draw a significant current from the speakers ( a few dozens of milliamps).
I'm unsure that my mod could introduce some crosstalk to the system?

 

[Tazio]

What is the point of connecting both channels to one VU meter?
Isn't it better for each channel to have its own

 

[Tazio]

There's no technical reason ...I got that nice looking VU-meter from a friend of mine for a couple of beers and I love the look of the front panel with that dancing needle on. That's all.
But having the balance control on the pre section, I wandered whether I could get it driven by both the channels.
I know there are commercial amplifiers featuring a single VU-meter ...

 

[Cbdb2]

Never connect 2 different amp outputs directly together. Imagine one amp trying to put out 1 volt and the other 2 volts, they will both try to source as much current as they can to put out those voltages but its impossible because they are tied together. IE large amounts of current going from the 2 volt amp to the 1 volt amp, often enough to burn up the output devices. I accidentaly did this with 2 bass guitar amps. The 300 watt amp caused smoke release from the 20 watt amp in a second or two.

 

[Cbdb2]

You can however include a resistor between each amp out and the VU with out a problem.

 

[DVDdoug]

Add another D1 & R1 for the other channel, also connected to C1, etc.

 

[sergeauckland]

You can however include a resistor between each amp out and the VU with out a problem.

That's right, provided the amp outputs aren't bridged and they share a common ground, you should be fine with something like 1k in series so buffering one channel from the other. Then adjust the variable resistor to get the meter dancing seductively.

S